A concentration of a biogenic substance such as glucose contained in a living body is measured on the basis of reflected light, scattered light, or transmitted light of light irradiated on the living body. More particularly, Raman scattering light of the biogenic substance is observed, and the concentration of the biogenic substance is calculated on the basis of the intensity of the Raman scattering light.
Patent Literature 1 and 2 disclose a method for measuring a glucose concentration optically. According to the method, first, a particle is implanted in the upper layer of a skin. The particle contains a reagent to react with glucose and to change a fluorescence property thereof. Next, the particle is irradiated with light having an exciting wavelength from the outside of the living body so as to measure fluorescence generated at the particle through the skin. On the basis of the measured fluorescence, the glucose concentration is measured.